1028 - Comparable Cosmetic Outcomes Across Racial and Age Groups After Dose-Escalated Five-Fraction Stereotactic Partial Breast Irradiation (S-PBI) on a Phase II Multicenter Trial
Presenter(s)
C. Bolton1, K. Fattah2, D. W. N. Kim3, M. Leitch4, D. D. M. Parsons2, E. M. Nichols5, W. Lu6, S. J. Becker7, P. G. Alluri2, C. R. Nwachukwu8, C. Ahn9, T. D. Chiu1, D. Farr4, R. Wooldridge4, S. Bahrami2, S. Stojadinovic2, R. D. Timmerman2, and A. S. Rahimi2; 1University of Texas Southwestern Medical Center, Dallas, TX, 2Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, 3Vanderbilt University Medical Center, Nashville, TN, 4Department of Surgery, University of Texas Southwestern Medical Center, Dallas, TX, 5Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, 6Medical Artificial Intelligence and Automation (MAIA) Lab, Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, TX, 7University of Maryland School of Medicine, Baltimore, MD, 8University of Texas Southwestern Department of Radiation Oncology, Dallas, TX, 9Kidney Cancer Program, Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX
Purpose/Objective(s):
We report results from a multi-institutional phase II study of dose-escalated five-fraction S-PBI for early-stage breast cancer following partial mastectomy using a cobalt stereotactic radiation system. The primary endpoint was 3-year patient-reported global cosmesis. An exploratory analysis evaluated whether race/ethnicity or age impacts patient- and physician-reported global cosmetic outcomes.Materials/Methods:
Patient eligibility included DCIS or invasive epithelial histologies, AJCC clinical stage 0–II disease, tumor size <3 cm, and negative surgical margins. A dose of 40 Gy in 5 fractions was delivered to CTV with a minimum dose of 30 Gy in 5 fractions to the PTV. CTV and PTV margins were 1 cm and 3 mm, respectively. For PTV cavity volumes >100 cc, dose was reduced to 35 Gy in 5 fractions to the CTV and 30 Gy in 5 fractions to the PTV. Global cosmesis was assessed using a 4-point scale (excellent, good, fair, poor). Ethnicity was categorized as Black/African American(BA), White/Hispanic(WH), or White/non-Hispanic(WN). Patients and physicians completed baseline and follow-up EORTC cosmesis questionnaires.Results:
From March 2019 to October 2021, 74 patients were treated; 38 received 40 Gy and 36 received 35 Gy. Median follow-up was 48 months (range, 2–64), and median age was 63 years (range, 43–77). There were 11/74 (15%) BA, 51/74 (68%) WN, and 9/74 (12%) WH patients. Cumulatively, patients reported excellent or good cosmesis in 29/43 (67.4%) BA, 32/35 (91.4%) WH, and 162/200 (81%) WN assessments at baseline, 12, 24, and 36 months post S-PBI. Physicians reported excellent or good cosmesis in 32/43 (74%) BA, 32/35 (91.4%) WH, and 171/200 (85.5%) WN assessments at the same timepoints. Kruskal–Wallis testing demonstrated no significant differences in cosmesis across timepoints among racial/ethnic groups (baseline p=0.554; 12 months p=0.319; 24 months p=0.293; 36 months p=0.348). Across age groups, patients reported excellent or good cosmesis in 18/24 (75%) for 40–49 years, 65/76 (85.5%) for 50–59 years, 77/100 (77%) for 60–69 years, and 71/84 (84.5%) for 70–79 years at same respective timepoints. Similarly, Kruskal–Wallis testing showed no significant differences between age groups (baseline p=0.766; 12 months p=0.430; 24 months p=0.087; 36 months p=0.955).Conclusion:
Our study demonstrates that judicious reduction of PTV margins using this technology enables excellent-to-good long-term cosmetic outcomes with dose-escalated therapy, with no statistically significant differences in cosmesis across racial/ethnic or age groups.